PROJECT SUMMARY/ABSTRACT Obstructive sleep apnea (OSA) and chronic insomnia are prevalent, debilitating, and challenging to treat, but their all too common co-occurrence amplifies morbidity and complicates the management of affected patients. Unfortunately, previous research provides limited guidance as to what constitutes the best and most practical management approach for this comorbid patient group. Various medications have FDA approval for insomnia management, but most have not been tested among comorbid OSA/insomnia patients. Moreover, many of these agents suppress respiratory drive making apnea symptoms worse, whereas others result in residual sedation, an unwanted side effect for the already sleepy OSA patient. Some promising preliminary data suggest that cognitive-behavioral insomnia therapy (CBT) may be a safe and effective adjunct to standard OSA therapies for comorbid OSA/insomnia. However, studies reporting these findings have included small patient samples, lacked both control groups and adequate follow-up periods, and failed to address how this promising therapy can be made more broadly accessible given the currently limited number of providers capable of delivering it. This dual-site randomized clinical trial will move the field forward by addressing the limitations of this previous studies. Specifically this project will use a ?SMART? design to test a stepped care model relative to standard positive airway pressure (PAP) therapy and determine if (1) augmentation of PAP therapy with OCBT improves short-term outcomes of comorbid OSA/insomnia; and (2) providing a higher intensity 2nd-stage CBT to patients who show sub-optimal short-term outcomes with OCBT+PAP improves short and longer-term outcomes. The 384 PAP-treated comorbid OSA\insomnia patients enrolled will complete baseline assessment with sets of syndrome-specific measures as well as global measures of sleep/wake functioning. They then will be randomly assigned to a treatment consisting of the UC alone or PAP +OCBT. After 8 weeks they will be reassessed with all measures taken at baseline. Patients reaching remission status (insomnia severity index score < 10 + Quebec Sleep Questionnaire mean item score > 5) will be offered no additional insomnia intervention but will continue PAP and complete study outcome measures again after an additional 8-weeks and again at 3 and 6 month follow-ups. OCBT recipients classified as ?unremitted? after 8-weeks of treatment will be re-randomized to a 2nd- stage treatment consisting of a continued, expanded engagement with the OCBT or a switch to a therapist- directed CBT (TCBT). Those receiving the 2nd-stage intervention as well as the UC group will be reassessed after another 8 weeks and then again at 3- and 6-month follow-up time points. Results should provide much new information that greatly enhances our knowledge about how to effectively treat comorbid OSA/insomnia patients and about the role of OCBT intervention in the short- and longer term management of this patient group.